One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read from or write to the disk.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult using conventional technology to quickly and accurately position the read/write head over the desired information tracks on the storage media. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
One approach that has been effectively used by disk drive manufacturers to improve the positional control of read/write heads for higher density disks is to employ a secondary actuator, known as a micro-actuator that works in conjunction with a primary actuator to enable quick and accurate positional control for the read/write head. Disk drives that incorporate a micro-actuator are known as dual-stage actuator systems.
Various dual-stage actuator systems have been developed in the past for the purpose of increasing the access speed and fine tuning the position of the read/write head over the desired tracks on high density storage media. Such dual-stage actuator systems typically include a primary voice-coil motor (VCM) actuator and a secondary micro-actuator, such as a PZT element micro-actuator. The VCM actuator is controlled by a servo control system that rotates the actuator arm that supports the read/write head to position the read/write head over the desired information track on the storage media. The PZT element micro-actuator is used in conjunction with the VCM actuator for the purpose of increasing the positioning access speed and fine tuning the exact position of the read/write head over the desired track. Thus, the VCM actuator makes larger adjustments to the position of the read/write head, while the PZT element micro-actuator makes smaller adjustments that fine tune the position of the read/write head relative to the storage media. In conjunction, the VCM actuator and the PZT element micro-actuator enable information to be efficiently and accurately written to and read from high density storage media.
One known type of micro-actuator incorporates PZT elements for causing fine positional adjustments of the read/write head. Such PZT micro-actuators include associated electronics that are operable to excite the PZT elements on the micro-actuator to selectively cause expansion or contraction thereof. The PZT micro-actuator is configured such that expansion or contraction of the PZT elements causes movement of the micro-actuator, which, in turn, causes movement of the read/write head. This movement is used to make faster and finer adjustments to the position of the read/write head, as compared to a disk drive unit that uses only a VCM actuator. Exemplary PZT micro-actuators are disclosed in, for example, JP 2002-133803, entitled “Micro-actuator and HGA” and JP 2002-074871, entitled “HGA Equipped with Actuator for Fine Tuning, Disk Drive Equipped with the HGA, and Manufacturing Method of the HGA.” Other exemplary PZT micro-actuators are also disclosed in, for example, U.S. Pat. Nos. 6,671,131 and 6,700,749.
FIGS. 1a-1b illustrate a conventional disk drive unit and show a magnetic disk 101 mounted on a spindle motor 102 for spinning the disk 101. A voice coil motor arm 104 carries a HGA 100 that includes a micro-actuator 105 with a slider 103 incorporating a read/write head. A voice-coil motor (VCM) is provided for controlling the motion of the motor arm 104 and, in turn, controlling the slider 103 to move from track to track across the surface of the disk 101, thereby enabling the read/write head to read data from or write data to the disk 101. In operation, a lift force is generated by the aerodynamic interaction between the slider 103, incorporating the read/write transducer, and the spinning magnetic disk 101. The lift force is opposed by equal and opposite spring forces applied by a suspension of the HGA 100 such that a predetermined flying height above the surface of the spinning disk 101 is maintained over a full radial stroke of the motor arm 104.
FIG. 2 illustrates the HGA 100 of the conventional disk drive device of FIGS. 1a-1b. The HGA 100 comprises a micro-actuator 105, a slider 103 disposed in the micro-actuator 105 and a suspension 113 to support the micro-actuator 105 and slider 103. The suspension 113 is manufactured by assembling a base plate 114, a hinge 115, a load beam 116 and a flexure 117. However, because of the inherent tolerances of the VCM and the head suspension assembly, the slider 103 cannot achieve quick and fine position control, which adversely impacts the ability of the read/write head to accurately read data from and write data to the disk. As a result, a PZT micro-actuator 105, as described above, is provided in order to improve the positional control of the slider and the read/write head. More particularly, the PZT micro-actuator 105 corrects the displacement of the slider 103 on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and/or head suspension assembly. The micro-actuator 105 enables, for example, the use of a smaller recording track pitch, and can increase the “tracks-per-inch” (TPI) value by 50% for the disk drive unit, as well as provide an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator 105 enables the disk drive device to have a significant increase in the surface recording density of the information storage disks used therein.
Referring to FIGS. 2a-2c, a conventional PZT micro-actuator 105 includes a ceramic U-shaped frame, which has two ceramic beams or side arms 107 each having a PZT element thereon. The ceramic beams 107 hold the slider 103 therebetween and displace the slider 103 by movement of the ceramic beams 107. The PZT micro-actuator 105 is physically coupled to a suspension tongue 122 of the suspension 113 (refer to FIG. 2c). Three electrical connection balls 124 (gold ball bonding or solder ball bonding, GBB or SBB) are provided to couple the micro-actuator 105 to the inner suspension traces 119 located at the side of each of the ceramic beams 107. In addition, there are four metal balls 125 (GBB or SBB) for coupling the slider 103 to the outer suspension traces 118.
Referring to FIG. 2c, the suspension tongue 122 is formed at one end of the flexure 117 and a step portion 123 is formed between the suspension tongue 122 and the flexure 117. The suspension tongue 122 has a micro-actuator mounting area 133 on which the micro-actuator is mounted by epoxy or ACF (anisotropic conductive film). The load beam 116 of the suspension 113 has a dimple 121 formed thereon that engages with the suspension tongue 122. The dimple 121 and the step portion 123 of the flexure 117 support the suspension tongue 122 cooperatively. The micro-actuator mounting area 133 of the suspension tongue 122 has layered structure that forms a step in conjunction with the epoxy or ACF. A parallel gap 126 is provided between the suspension tongue 122 and the micro-actuator 105 to allow the micro-actuator 105 to smoothly displace the slider 103 when a voltage is input to the PZT elements of the micro-actuator 105. The gap 126 can assure a free movement of the slider 103 and the micro-actuator 105, which is very important for HGA performance.
It is proved by experiments that the micro-actuator and the slider can obtain a good work performance, such as dynamic and static performance when the parallel gap 126 has a distance ranges between 35 μm and 50 μm. Hence, keeping the parallel gap 126 with a height of 35-50 μm has critical effect to performance improvement of the micro-actuator and slider. However, conventional HGA cannot form such a step with a height ranging between 35 μm and 50 μm. More specifically, as shown in FIG. 2d, the micro-actuator mounting area 133 of the suspension tongue 122 has a laminated structure made of a polyimide base layer 129 disposed on surface of the suspension tongue 122, a conductive layer 130 disposed on the polyimide base layer 129 and a polyimide cover layer 131that covers the conductive layer 130. The polyimide base layer 129 has a thickness of 10 μm, the conductive layer 130 has a thickness of 10 μm, while the polyimide cover layer 131 has a thickness of 3-5 μm, therefore, the layered structure has a total thickness of about 23-25 μm. When the micro-actuator is mounted on the layered structure of the mounting area by epoxy or ACF, since the epoxy or ACF has a maximal thickness of 5 μm, the parallel gap formed between the assembled micro-actuator and the suspension tongue ranges between 28 μm and 30 μm; in addition, effected by various tolerances existing in manufacturing process, the micro-actuator and the suspension tongue may not work properly because the gap formed therebetween is too small, thus influencing operation performance of the micro-actuator and the HGA.
Moreover, as illustrated in FIG. 2c, the HGA need have suitable static attitude angle to avoid tilt of the micro-actuator and the HGA during HGA assembling process, thus not influencing operation performance of the micro-actuator and the HGA. Since the dimple 121 of the load beam 116 of the suspension 113 supports the top end of the suspension tongue 122, conventionally, a step 128 (may be formed such as by machining a sheet of material using stamping process and then bending it slantways) is formed between the other end of the suspension tongue 122 and welding point of the flexure 117 by suitable manner. The step 128 and the dimple 121 of the load beam 116 support the suspension tongue 122 together. However, due to certain manufacture precision limitation, along with very small dimension (a step height of not more than 50 μm) of the part to be machined (the step), this conventional structure design, i.e., integral structure of the flexure and the suspension tongue by forming an inclined step using bending process, brings difficulty of machining, thereby increasing manufacture cost.
Thus, there is a need for an improved HGA and disk drive unit that does not suffer from the above-mentioned drawbacks.